The proposed research will study the phenomenon that presenting food pellets to hungry rats generates consumption of inordinately excessive quantities of fluid. This phenomenon was first reported by Falk (1961) who called it "schedule-induced polydipsia" (SIP). He suggested that SIP represents a new behavioral classification since it appeared inexplicable in terms of physiological mechanisms and failed to fall easily into the two traditional behavioral classifications, operant and respondent. Research has since demonstrated, however, that SIP is affected by its consequences, the defining criterion for operant behaviour. It is the purpose of the present experiment to determine whether systematic variation in the consequences of drinking affects SIP in the same quantitative manner as it does operant behavior. Herrnstein (1970, 1974) has described an equation which provides a remarkably good description of how rate of operant behavior changes as a function of variation in amount, rate, and delay of reinforcement. The proposed experiment will vary amount of water reinforcement and determine if Herrnstein's equation adequately describes changes in the rate of SIP. Obtaning such quantitative data is a logical step in investigating whether SIP represents a special class of behavior. The results of this experiment also have implications for the use of the SIP paradigm as an experimental analogue of such excessive/compulsive behavior an alcohol consumption.